The geoblogosphere – and the rest of the news – have been buzzing with information and discussion about the recent M8.9 earthquake in Japan. Despite being a country that is relatively well-prepared for events like these, even Japan couldn’t withstand the power of such a quake and the resulting tsunami, and they will need help. Please consider donating to a relief organization such as the Red Cross, Doctors Without Borders, or Save the Children.

Erik Klemetti over at the Eruptions Blog mentioned the new eruption at Karangetang volcano in Indonesia, which occurred just after the earthquake in Japan – and made the point that the two events probably aren’t linked (since the volcano was already showing signs of unrest). This is likely the case in most situations where eruptions occur in close timing with earthquakes – so the answer to the question of “Did this earthquake cause an eruption?” is, probably not. But that still leaves this question: Can earthquakes trigger eruptions? This is the main subject of a paper I read recently: Manga, M. and Brodsky, E., 2006, Seismic Triggering of Earthquakes in the Far Field: Volcanoes and Geysers.

The answer is, predictably, complicated. Studies have indicated that eruptions do occur in the vicinity of large earthquakes more often than would be expected by chance – at least on the short term (within 5 days). But this only appears to be true for a very small percentage of eruptions, and only with the largest earthquakes (which implies that the stress changes caused by earthquakes are small compared to the stress changes needed to initiate eruptions). This works out to <<1% of eruptions.

Manga and Brodsky, assuming that very large earthquakes could trigger eruptions, set out to describe how this could occur. They divide triggers into two categories: mechanisms which increase the overpressure within the magma (something like shaking a bottle of soda until it explodes), and mechanisms that could trigger eruptions from outside the magma chamber. (There are a few suggestions made in the paper that I’m leaving out, because the authors make a point of saying that their effects are not strong enough to make them plausible eruption triggers – the criteria is that a mechanism must produce at least a 10 MPa overpressure).

From within the magma,

Bubble nucleation: Creating new bubbles by increasing the nucleation rate through pressure differences caused by the passage of seismic waves. This mainly depends on the melt being supersaturated with gas to begin with; if seismic waves cause new bubbles to form, large gas pressures compared to the ambient (magma) pressure may cause bubbles to grow quickly and explosively.

Falling roofs: Aggregates of crystals (or crystal “mushes”) formed near the roofs of magma chambers could be shaken loose by seismic waves; the sinking crystals could initiate convection in the chamber, bringing hotter magma to the top. This magma could vesiculate and expand as it rises, creating overpressures and possibly initiating an eruption. This mechanism depends on the actual existence of crystal “mushes” (hard to observe directly), as well as the velocity of their descent being great enough that they initiate overturn on a short timescale.

From outside the magma chamber,

Surface unloading: If a distant earthquake was strong enough to shake loose an already weak part of a volcanic edifice and cause a landslide, it could effectively “uncork” a pressurized magma chamber and initiate an eruption. (This is essentially what happened in the 1980 eruption of Mount St. Helens, although the earthquake that accompanied that eruption was not distant or particularly large.) This mechanism has never been observed in relation to distant earthquakes, but it’s plausible if the volcano is weak enough.

Fatigue and crack growth: Repeated or fluctuating stresses are known to cause material fatigue and cracking before the normal failure stress is reached. This could be somewhat related to the previous mechanism (in that large cracks could then cause surface unloading), or it could create rifts that magma could exploit to form dikes and initiate rift eruptions (like what’s happening at Pu’u O’o right now). The authors note that this would require very high pore pressures in something like a volcanic hydrothermal system, and even then earthquakes could trigger eruptions via this mechanism only 0.01% of the time.

What is the upshot of all this hypothesizing? Basically, it’s that very large earthquakes could trigger eruptions, but we don’t yet know exactly how – and that it will require a great deal of careful monitoring and study to possibly catch these mechanisms in action. Because we can’t yet say for sure whether these mechanisms actually occur, it’s silly to immediately start speculating about a link between the recent Japan earthquake and any eruptions that are occurring right now. For the moment, it’s important to remember that any natural hazard requires careful monitoring all on its own – whether or not there seems to be an upswing in the occurrence of other natural events nearby. This means that things like earthquake activity, tsunamis, and volcanic eruptions should be paid attention to all the time – not just when it seems like more of them are happening.

Comments

9 Comments

This is an interesting review of the likely short-term ways that an earthquake could trigger a specific eruption. I’d love to see a follow-up piece on the scientific evidence for longer term (weeks to years) triggering of volcanic eruptive episodes. There’s certainly a fair amount of anecdotal evidence of instances of large eruptions (e.g., Pinatubo) following large quakes by months to years, if I’m not mistaken. It’d be interesting to see if this is purely coincidental or whether there’s a scientifically established linkage between events like this. At least one volcano blogger has already invoked this relationship with an eye on future eruptions in central Japan.

A couple of years ago I blogged about a study of how historic volcanic activity in the Andes compared with seismic activity on the adjacent subduction zone: the authors argued that volcanic activity was boosted in the 6-12 months following large earthquakes on the subduction zone – some of the time, anyway.

Thanks for mentioning the post! That was one of the papers that came up when I started pulling up research on long-term triggers for eruptions. I’ll be glad to have your take on it as well as the authors’.

I had come across a paper over the summer when I was teaching Earthquakes and Volcanoes that indicated an increased rate of eruptive activity in the year following a major earthquake. It might be the same one that Chris is mentioning though. I will have to look it up.

This is certainly an interesting topic for discussion. The cyclic strain from a large magnitude event like in Sendai will certainly affect magma movement in the sub-surface. The question is what is the delay time, bearing in mind the strain release and accomodation in the local area. There is also the issue of new or larger magma conduits which can open following lare earthquakes. Is there some documentation of such like ftrom monitoring e.g. Kileau or Mt. Unzen?

Some of my colleagues at the Istituto Nazionale di Geofisica e Vulcanologia in Catania have recently published work on the effect of more or less distant major earthquakes on the dynamics of Mount Etna in Sicily: Cannata et al. (2010): Response of Mount Etna to dynamic stresses from distant earthquakes, J. Geophys. Res., vol.115, B12304, http://dx.doi.org/10.1029/2010JB007487. These authors document unrest in early 2006 (culminating in a large phreatic explosion at the summit of Etna) shortly following a M 6.8 quake in Greece, and the onset of a long-lasting flank eruption on 13 May 2008, one day after the devastating M 7.9 Sichuan (China) earthquake.
Etna is in a new period of intermittent eruptive activity since January 2011, which thus far has consisted of two episodes of spectacular lava fountaining from the Southeast Crater at Etna’s summit on 12-13 January and 18 February. Obviously, we were all curious to see whether the 11 March 2011 M 9 earthquake in Japan would have any effect on the dynamics of Etna and maybe help get a third episode of lava fountaining get under way. Now, ten days have passed since the quake, but Etna has not shown any significant variation in its seismic and volcanic activity thus far. Certainly, no immediate responses as in the cited cases of 2006 and 2008 have occurred. In my opinion this underlines how really close a volcano must be to erupting in order to show a distinct effect of (that is, having its eruption triggered by) a major earthquake somewhere nearby or farther away.

I guess we would fare best in keeping our eyes on volcanoes that we consider potentially dangerous and wait for THEM to give us warning signs rather than expecting to get any clues from a major earthquake somewhere, which might or might not trigger some eruption somewhere over here or somewhere else.

Thanks for the reference! I was interested in the spatial relationships as well as the temporal, and I had wondered what the distance limits were on this sort of triggering. (I had suspected there was probably a limit to triggering distances – otherwise a lot more “triggered” eruptions would be showing up in the statistical analyses I’ve seen. The fact that it’s usually larger earthquakes which do the triggering also made me think that distance was a limiting factor.)

I agree with your conclusions about monitoring – while the triggering phenomenon is pretty fascinating, it’s definitely not practical in the immediate sense to be trying to connect earthquakes and eruptions.

About Jessica

Jessica Ball is a Mendenhall Postdoctoral Fellow at the U.S. Geological Survey, researching stratovolcano hydrothermal systems and how they affect volcano stability. She previously worked at the Geological Society of America's Washington DC Policy Office, learning about the intersection of Earth science and legislative affairs. Her PhD in volcanology focused on how water affects the stability of cooling lava domes, and involved both field investigations and numerical modeling applications. Her blogging covers a range of topics, from her experiences in academic geosciences to science outreach and communication to her field and lab work in volcanology.

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